People working off the electricity grid (soldiers, first responders, humanitarian relief workers, etc.) need to be able to generate their own electricity. Rome described in U.S. Pat. Nos. 7,851,932 and 6,982,497 (the contents of which are incorporated herein by reference) electricity-generating backpacks that provide human-generated electricity. The electricity-generating backpacks include a mass, an adjustable spring, and a generator to remove electricity. The devices enable a human to drive the kinetic movement of the spring-mass system.
The afore-mentioned electricity generating backpacks have been found to be quite useful to meet the electricity needs of soldiers, such as Marines. To determine effectiveness, one has to determine the daily electricity usage budget of the typical soldier as well as the daily electricity production budget. One recent estimate determined that Marines use an average of 5 W of electricity. Over a 24 hour period, this corresponds to 4.32*105 Joules or 120 Watt-hours of electricity. To generate this level of electricity, the product of electrical power and the duration over which it is produced must be determined. If it is assumed that a mission might take 4-10 hours of walking and generate 8-20 W over that time, that is equivalent to 32-200 Watt-hours of electricity. However, if the only source of power from the backpack was generated during walking, there may be some days where the user does not walk enough to generate the necessary power to keep the batteries fully charged. A modification is thus desired whereby a user may use the electricity generating backpack to generate electricity without walking. The present invention is designed to meet this need.